Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Sound: missed test questions

  1. Jun 28, 2003 #1

    Dx

    User Avatar

    1) A sample of Co2 contains 3.01x10^23 molecules at STP. what volume does this sample occupy?
    I have the multiple choice answers but need help explaining why you chose that answer.

    11.2L
    44.8L
    32.7L


    2) a 25L container hold H gas at gauge pressure 1.25atm and temo 0 degrees celcius. whats mass of H in this container

    2.8g
    4.2g
    5.6g

    3) An ideal gas has density of 1.75kg/m^3 at gauge pressure 160kPa. what must be the gauge pressure isf density of 1 kg/m^3 is desired at the same temp?

    356kPA
    280kPA
    48KPa

    4) an ideal gas in container of volume 100cm^3 at 20 degrees C has pressure of 100N/m^2. determine the number of gas molecules in the container

    6x10^23
    2.5x10^18
    5.2x10^18

    I am not going to put my work here since ive already missed them. I cant go on not understanding why or what these answers were. I have gone back to re-read the chapter on this and still unclear with the ideal gas law, i know its said to be simple but its not clicking here. I dont need a long explaination just the answer you got and briefly how you derived it. If you feel you dont have to answer this cause it vilates so rules its like i said "Its not homework but missed test questions that for my own personnel conquest I must try to solve but need your help, plz" Please understand I hold each of you in the highest respect and thank you for all youve done. Its really been a great help for me to better understand this subject.
    I applaude you all!
    Dx :wink:
     
  2. jcsd
  3. Jun 28, 2003 #2

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    You use the same equation for all of these: PV=nRT

    P=absolute pressure
    V=volume
    n=# of moles
    R=ideal gas constant
    T=temp (in oK)
     
  4. Jun 28, 2003 #3

    Tom Mattson

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Hey, check this out:

    http://www-tech.mit.edu/Chemicool/idealgas.html [Broken]

    Neato.
     
    Last edited by a moderator: May 1, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook